12/19/2023 0 Comments Precipitate tests![]() ![]() Incubate all test tubes for 30 minutes at 37☌.Tilt the test tube to prevent mixing of the sera, and allow the antiserum to run down the side of the test tube.Carefully overlay all four test tubes with 0.3 ml of bovine globulin antiserum.Transfer 0.3 ml of saline into the test tube labelled as control by using a clean 0.5-ml pipette.Transfer 0.3 ml of each of the normal bovine serum dilutions into its appropriately labelled test tube by using a different 0.5-ml pipette.Label three serological test tubes according to the antigen dilution to be used (1:25, 1:50, and 1:75) and the fourth test tube as a saline control.Normal bovine serum diluted to 1:25, 1:50, and 1:75 with physiological saline. ![]() The visible precipitate ring is formed at zone of equivalence. The insufficient amount of antigen gives rise to zone of antibody excess and excessive amounts of antigen will give rise to zone of antigen excess. To determine the precipitation reaction, a series of dilutions of the antigen is used because both insufficient and excessive amounts of antigen will prohibit the formation of a visible precipitate.The rate at which the visible ring forms relies on the concentration of antibodies in the serum and the concentration of the antigen. After a period of incubation of up to 4 hours, a ring of precipitate is visible at the point of contact (interface) in the presence of the antigen-antibody reaction. Antiserum is injected into a small-diameter test tube, and the antigen is then carefully added to form a discrete upper layer. This antigen-antibody reaction can be indicated by the formation of a visible precipitate, a flocculent or granular turbidity, in the test fluid. The ring or interfacial test is a simple serological method that exemplifies the precipitin reaction in solution.
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